Ultrasonic diagnostic apparatus

Abstract

In an ultrasonic diagnostic apparatus using an array type transducer probe, wherein improved tomographic image resolution is desired by electronically focusing ultrasonic wave toward an object to be examined in both directions, i.e., the array direction and the lens direction. During first scanning of the ultrasonic transducer array in the array direction, the signals received from the probe are synthesized in phase with respect to each other via delay lines having predetermined delay times to obtain first scanned signals in real time, so that focusing the reflected ultrasonic wave can be electronically accomplished in the array direction. After this first scanning, the probe is mechanically moved to a given position in the lens direction normal to the array direction. Then a second scanning operation is accomplished to obtain similar first scanned signals. All of the first scanned signals are processed by a delay time control circuit, digitized, and then stored. Finally, all of the stored first scanned signals are read out and synthesized in phase with respect to each other by an adder circuit to obtain second scanned signals, so that focusing the reflected ultrasonic wave can be accomplished in the lens direction. The resultant second scanned signals are converted into analogue signals to be displayed as a tomographic image of the desired diagnostic part in the object.

What is claimed is: 
     
       1. An ultrasonic diagnostic apparatus for examining an object by utilizing ultrasonic waves, comprising: ultrasonic probe means including a plurality of ultrasonic transducer elements aligned in a line parallel to a first scanning direction for emitting fan-shaped ultrasonic waves;   first control means for controlling the probe means to electrically scan the object by the fan-shaped ultrasonic waves in said first scanning direction such that a predetermined number of said transducer elements are excited to transmit the ultrasonic waves toward the object and ultrasonic echoes reflected from the object are derived as a plurality of echo signals from the transducer elements after first delay time corrections are given;   first synthesizing means for electrically synthesizing said plurality of echo signals with an in-phase condition so as to derive a plurality of first scanning signals, whereby electrical focusing is achieved in the first scanning direction;   means for mechanically and intermittently moving the ultrasonic probe means along a second scanning direction perpendicular to the first scanning direction so as to obtain said first scanning signals at given scanning positions over the second scanning direction;   memory means for storing said plurality of first scanning signals derived from the first synthesizing means;   second control means for controlling the memory means to read out said plurality of first scanning signals with second delay time corrections; and   second synthesizing means for electrically synthesizing said plurality of first scanning signals with an in-phase condition so as to derive a plurality of second scanning signals, whereby electrical focusing is achieved in the second scanning direction.   
     
     
       2. An apparatus as claimed in claim 1, wherein: said first control means includes a plurality of analogue switches, a plurality of delay lines having variable delay times and connected via the respective analogue switches to respective of said plurality of ultrasonic transducer elements, and a scanning control circuit for selecting said analogue switches to be actuated and also said first delay times of the delay lines for said first delay time corrections;   said memory means includes a plurality of random access memories;   said second control means includes a delay time control circuit for designating addresses of said random access memories so as to read out said plurality of first scanning signals with said second delay time corrections; and   said second synthesizing means includes an adder for summing said plurality of first scanning signals read out from said plurality of random access memories so as to derive said second scanning signals.   
     
     
       3. An apparatus as claimed in claim 2, further comprising: an envelope detector for detecting said second scanning signals derived from said adder;   a frame memory for storing said envelope-detected second scanning signals so as to obtain a tomographic image signal of the object; and   monitor means for displaying a tomographic image of the object based upon said tomographic image signal.   
     
     
       4. An apparatus as claimed in claim 3, wherein only the first scanning signals acquired from a scanning portion within the object in a given depth from a surface of the object are read out from said random access memories by said second control means, whereby a C-mode tomographic image is displayed on said monitor means. 
     
     
       5. An apparatus as claimed in claim 1, wherein said ultrasonic probe means comprises: a curved surface for diverging the ultrasonic waves toward the object in the second scanning direction.   
     
     
       6. An ultrasonic diagnostic apparatus as claimed in claim 1, wherein said ultrasonic probe means comprises: an acoustic lens for diverging the ultrasonic waves toward the object in the second scanning direction.   
     
     
       7. An ultrasonic diagnostic apparatus for examining an object by utilizing ultrasonic waves, comprising: ultrasonic probe means including a plurality of ultrasonic transducer elements aligned in a line parallel to a first scanning direction;   first control means for controlling the probe means to electrically scan the object by the ultrasonic waves in said first scanning direction such that a predetermined number of said transducer elements are excited to transmit the ultrasonic waves toward the object and ultrasonic echoes reflected from the object are derived as a plurality of echo signals from the transducer elements after first delay time corrections are given;   first synthesizing means for electrically synthesizing said plurality of echo signals with an inphase condition so as to derive a plurality of first scanning signals, whereby electrical focusing is achieved in the first scanning direction;   means for mechanically and intermittently moving the ultrasonic probe means along a second scanning direction perpendicular to the first scanning direction so as to obtain said first scanning signals at given scanning positions over the second scanning direction;   pulse generation mean including a π/2 phase shifter for producing first pulse signals and second pulse signals via the π/2 phase shifter, said first pulse signals having a phase different by π/2 from that of said second pulse signals;   a first combination of signal mixing and storing means for multiplying said first scanning signals from said first synthesizing means by said first pulse signals and for temporarily storing first mixed scanning signals;   a second combination of signal mixing and storing means connected parallel to said first combination for mixing said first scanning signals with said second pulse signals and for temporarily storing second mixed scanning signals; and   signal processing means for performing convolutions on said first and second mixed scanning signals, whereby electrical focusing is achieved in the second scanning direction.   
     
     
       8. An apparatus as claimed in claim 7, wherein: said first control means comprises a plurality of analogue switches connected to the respective transducer elements; and   said storing means of said first and second combinations comprises random access memories.   
     
     
       9. An apparatus as claimed in claim 8, further comprising: a frame memory for storing said second scanning signals so as to obtain a tomographic image signal of the object; and   monitor means for displaying a tomographic image of the object based upon said tomographic image signal of the object.   
     
     
       10. An apparatus as claimed in claim 9, wherein only the first scanning signals acquired from a scanned portion within the object in a given depth from a surface of the object are read out from said random access memories, whereby a C-mode tomographic image is displayed on said monitor means. 
     
     
       11. An apparatus as claimed in claim 7, wherein said ultrasonic probe means comprises: a curved surface for diverging the ultrasonic waves toward the object in the second scanning direction.   
     
     
       12. An apparatus as claimed in claim 7, wherein said ultrasonic probe means comprises: an acoustic lens for diverging the ultrasonic waves toward the object in the second scanning direction.